The Gory Sowie Terrane: a key to understanding the Palaeozoic evolution of the Sudetes area and beyond

Abstract

In the light of various recent data, the Góry Sowie metamorphic complex (GSMC) area should be considered to represent a thrust-nappe fragment of the Góry Sowie Terrane (GST) preserved within the Sudetic mosaic-like structure. Distinct structural-metamorphic history of the GSMC in comparison to the adjacent Saxothuringian and Moldanubian metamorphic areas (terranes) suggests that described complex is a detached fragment of the GST. The GSMC is the only area in the Sudetes with Caledonian deformations which are documented radiometrically. The oldest detrital zircons that have been recognized so far from the Sudetic metamorphic complexes, are documented by isotopic dating of the GSMC. They are of the Early Proterozoic or even Archean ages. The zircons may have come from a part of Baltica. The GSMC is herein considered to be a detached thrust-nappe relict of a Caledonian magmatic arc (GSA) thrusted into the northeastern periphery of the Bohemian Massif. This arc developed on the southwestern margin of Baltica (recent geogmphical reference). During the Caledonian orogeny (Late Ordovician/Early Silurian), the GST was amalgamated with the East Avalonia Terrane, and the closure of the Tornquist Ocean took place. Later on, during the Variscan orogeny (Late Devonian), a fragment of the GST i.e. GSMC, was thrusted towards SSW over an obducted, also towards SSW, ophiolitic dismembered fragments derived from the Tornquist Ocean. Almost a 20 years old suggestion expressed by Prof. J. Znosko that the GSMC is underlain by ophiolitic rocks is still valid. The GSMC itself conceived as a SW fragment of a Caledonian terrane (GST) may point out that the Caledonian orogenic belt does occur in central and southern Poland.